A wheeled crane is a full-circle slewing crane in which a hoisting operation part is installed on a specially-made chassis, and has the advantages of being flexible and convenient for transition and so on. The wheeled crane is an important part of crane equipment, and mainly includes truck cranes, all-terrain cranes, mobile cranes and other products. The products have the advantages of good flexibility, fast transition, high operation efficiency and the like; but part of the products (e.g., the truck cranes) must be supported by supporting legs during working, cannot travel with load and are not suitable for working on soft or muddy fields. Although part of the products (e.g., the mobile cranes) can achieve tire supported operations and travel with load, due to the limitations of the carrying capacity of tires and axles and the larger ground pressure, the requirements for the ground conditions are higher, and the performance is lower in general.
A track crane is a swing arm rotary crane in which the hoisting operation part is installed on a track chassis. It walks depending on a track attachment, has a large grounding area, good trafficability and strong adaptability and can travel with load. Due to its structural limitations, the damage of the track to the pavement is larger, thus the track crane cannot travel on roads. Moreover, the travelling speed of the track crane is low, so the track crane needs to be detached and carried by other vehicles when transferred to other construction sites, and the track crane needs to be re-assembled on another construction site, therefore the working efficiency is low, the transport cost is high, the application range is small, and the limitation is larger.
In the prior art, there has been a technical solution of adding a detachable track structure on the existing wheeled crane to quickly change the wheeled crane into a track crane so as to meet the hoisting operation requirements of different pavement conditions, expand the application range of the product and achieve multiple objectives of one crane.
As shown in FIG. 1A and FIG. 1B, one technical solution of adding a track attachment on the wheeled crane in the prior art is shown, a first connecting device 2′, a second connecting device 3′ and a connecting cross beam 4′ are added on a chassis 1′ of the wheeled crane in a building block manner so as to achieve force transfer, and a universal track 5′ of the track crane is adopted for connection so as to achieve the conversion of the wheeled crane and the track crane.
The specific implementation process of the above-mentioned technical solution is as follows:
1) As shown in FIG. 2, the first connecting device 2′ is lifted to a bottom surface of a race of the chassis 1′ by an auxiliary oil cylinder 6′, and a bolt connecting hole on the first connecting device 2′ is aligned to the bolt connecting hole on the race and is fixed by a bolt.
2) As shown in FIG. 3, the second connecting device 3′ is lifted by the auxiliary oil cylinder 6′, and a connecting hole 31′ on the second connecting device 3′ is aligned to a connecting hole 21′ on the first connecting device 2′ and then is fixed by propelling a locking shaft by a locking oil cylinder.
3) As shown in FIG. 4, the connecting cross beam 4′ is connected with the second connecting device 3′ by a bolt, and so far, the structure and the position of the connecting cross beam 4′ are the same as those of a cross beam of a conventional track crane.
4) As shown in FIG. 5, the connection mode of the connecting cross beam 4′ and the track 5′ is a conventional connection mode of the track crane, and so far, the conversion from the wheeled crane to the track crane is accomplished.
In the above-mentioned technical solution, after a vehicle frame of the wheeled crane is assembled with the first connecting device 2′, the second connecting device 3′ and the connecting cross beam 4′, the structure and the position of the connecting cross beam 4′ are the same as those of the conventional track crane, that is, the track can be installed according to the track installation steps of the conventional track crane. The first connecting device 2′ and the second connecting device 3′ can also be integrated, they are difficult to detach because they are connected with vehicle frame by bolt and are not detached in general in the state of the wheeled crane, and if the first connecting device and the second connecting device are split, the equipment weight in the transport state of the wheeled crane can be effectively reduced, and the travelling ability is improved.
The above-mentioned technical solution of adding the detachable track structure on the existing wheeled crane has the following shortcomings:
1) The track of the conventional track crane is adopted in the track connection, and the stress of the entire crane needs to be transferred from the race of the vehicle frame to the track during the operation in a track state. As the cross beam of the track is horizontally arranged, due to the structural limitation, the distance between the bottom surface of the race of the wheeled crane and the cross beam is quite large, the transfer distance is large, and the first connecting device and the second connecting device are arranged to counteract the distance. As the connecting devices bear all the working loads, when such a long distance connection is performed, the weight of a state conversion device is too large, and the working performance of the track crane state is reduced.
2) The connecting devices are located below the race, even if the supporting legs of the crane are lifted up, due to the relationship between related components of the chassis, the operation space is very narrow, and thus the installation is difficult.
3) The connecting devices usually adopt the connection mode of bolts and pin shafts, so high manufacturing precision at matching structure sites is required; and in addition, the connection points of bolt connection are numerous, resulting in a long installation time and increased fault points.